Local electronic structure of LiFePO4 nanoparticles in aged Li-ion batteries.
S. C. Nagpure, S. S. Babu, B. Bhushan, A. Kumar, R. Mishra, W. Windl, L. Kovarik, M. Mills, Acta Mater. 59, 69147 (2011).
The advanced LiFePO4 cathode based Li-ion batteries have shown potential for applications in electrification of automobiles. The rate capabilities of these batteries have been improved by the development of LiFePO4 nanoparticles. Here the effect of aging of Li-ion batteries on the local electronic structure of these LiFePO4 nanoparticles has been investigated with high resolution scanning transmission electron microscopy imaging. The local compositional changes within particles from unaged and aged batteries have been measured from electron energy loss spectroscopy (EELS) on these LiFePO4 nanoparticles. Further, the Z + 1 approximation within the density functional theory (DFT) framework has been employed to theoretically compute the energy loss near edge structure of LiFePO4. The measured EELS spectra are compared with the computed O K edge and Fe L2,3 edge to understand the loss of active Li from the host LiFePO4 structure in the aged battery, which corresponds to loss of capacity of the battery.